U.S. patent number 8,505,336 [Application Number 11/820,390] was granted by the patent office on 2013-08-13 for azs refractory composition.
This patent grant is currently assigned to Magneco/Metrel, Inc.. The grantee listed for this patent is Michael W. Anderson, Charles W. Connors, Sr., Shirish Shah. Invention is credited to Michael W. Anderson, Charles W. Connors, Sr., Shirish Shah.
United States Patent |
8,505,336 |
Connors, Sr. , et
al. |
August 13, 2013 |
AZS refractory composition
Abstract
A refractory composition includes a first set of components and
a colloidal silica binder. The first set of components includes
alumina and zirconia. The colloidal silica binder is provided at 5
wt % to 20 wt % of the dry weight of the first set of components.
The refractory composition includes 45 wt % to 75 wt % alumina, 15
wt % to 30 wt % zirconia, and 10 wt % to 30 wt % silica.
Inventors: |
Connors, Sr.; Charles W.
(Wilmette, IL), Anderson; Michael W. (West Chicago, IL),
Shah; Shirish (Carol Stream, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Connors, Sr.; Charles W.
Anderson; Michael W.
Shah; Shirish |
Wilmette
West Chicago
Carol Stream |
IL
IL
IL |
US
US
US |
|
|
Assignee: |
Magneco/Metrel, Inc. (Addison,
IL)
|
Family
ID: |
40135084 |
Appl.
No.: |
11/820,390 |
Filed: |
June 19, 2007 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20080314085 A1 |
Dec 25, 2008 |
|
Current U.S.
Class: |
65/27 |
Current CPC
Class: |
C04B
28/24 (20130101); C04B 35/106 (20130101); F27D
1/0006 (20130101); C03B 5/43 (20130101); C04B
35/66 (20130101); C04B 28/24 (20130101); C04B
14/303 (20130101); C04B 14/306 (20130101); C04B
20/008 (20130101); C04B 2235/3418 (20130101); C04B
2235/3244 (20130101); C04B 2111/00146 (20130101); C04B
2235/3217 (20130101); C04B 2235/5427 (20130101); C04B
2111/00551 (20130101) |
Current International
Class: |
C03B
5/43 (20060101) |
Field of
Search: |
;65/27 ;501/105 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
509950 |
|
Jul 1971 |
|
CH |
|
2738974 |
|
Mar 1978 |
|
DE |
|
198 45 761 |
|
Apr 2000 |
|
DE |
|
0 193 751 |
|
Sep 1986 |
|
EP |
|
0 298 860 |
|
Jan 1989 |
|
EP |
|
1428807 |
|
Jun 2004 |
|
EP |
|
2241512 |
|
Mar 1975 |
|
FR |
|
967934 |
|
Aug 1964 |
|
GB |
|
993161 |
|
May 1965 |
|
GB |
|
1184729 |
|
Mar 1970 |
|
GB |
|
1194158 |
|
Jun 1970 |
|
GB |
|
1283692 |
|
Aug 1972 |
|
GB |
|
10212158 |
|
Aug 1998 |
|
JP |
|
Other References
Extended European Search Report, PCT/US2008/067197, Jun. 9, 2011.
cited by applicant .
Schulle, W., "Feuerfeste Werkstoffe", Jan. 1, 1990, pp. 224-225,
XP002638439, ISBN 3-342-00306-5. cited by applicant .
International Search Report, PCT/US2008/067197, Sep. 1, 2008. cited
by applicant .
International Preliminary Report on Patentability,
PCT/US2008/067197, Dec. 22, 2009. cited by applicant .
Office Action, issued in Japanese Patent Application No.
2010-513355, dated Jan. 23, 2013. cited by applicant.
|
Primary Examiner: Del Sole; Joseph S
Assistant Examiner: Snelting; Erin
Attorney, Agent or Firm: Brinks Hofer Gilson & Lione
Claims
The invention claimed is:
1. A method of preparing a refractory, comprising: providing a
first set of components comprising alumina and zirconia, wherein
the first set of components comprises 35 wt % to 55 wt % alumina
particles and 25 wt % to 45 wt % zircon particles, and wherein the
zirconia comprises a first portion having a larger particle size,
the first portion comprising zircon sand and a second portion
having a smaller particle size, the second portion comprising
zircon flour; and providing a colloidal silica binder at 5 wt % to
20 wt % of the dry weight of the first set of components, mixing
the first set of components with the colloidal silica binder to
form a refractory composition comprising 55 wt % to 65 wt %
alumina, 20 wt % to 25 wt % zirconia, and 15 wt % to 25 wt %
silica; and forming a monolithic refractory composition on a
surface of a furnace.
2. The method of claim 1 wherein the furnace is a glass
furnace.
3. The method of claim 1 wherein the furnace is a brass
furnace.
4. The method of claim 1 wherein the refractory composition does
not include an effective amount of a hydraulic cement.
5. The method of claim 1 wherein the first set of components
comprises less than 5 wt % fused AZS particles.
6. The method of claim 1 wherein the first set of components
comprises 30 wt % to 50 wt % alumina particles of mesh size
8.times.14 and 2 wt % to 10 wt % alumina particles of mesh size
-14M.
7. The method of claim 1 wherein the first set of components
comprises alumina particles with an average particle size greater
than 1 mm.
8. The method of claim 1 wherein the silica binder is at 6 wt % to
12 wt % of the dry weight of the first set of components.
9. The method of claim 1 wherein the refractory composition is
formed by a method selected from casting, pumping, and
shotcreting.
10. The method of claim 1 further comprising the step of contacting
the refractory composition with molten glass.
11. The method of claim 1 wherein the first set of components
comprises about 45.7 wt % alumina and about 34.4 wt % zircon.
12. The method of claim 1, wherein at least 50% of the first set of
components includes particles greater than 400 microns.
13. The method of claim 1, wherein the first set of components
comprises 30 wt % to 40 wt % zircon.
14. The method of claim 1, wherein the refractory composition
comprises about 60 wt % alumina, about 22 wt % zirconia, and about
18 wt % silica.
15. A method of preparing a refractory, comprising: providing a
first set of components comprising alumina and zirconia, wherein
the median particle size of the first set of components is greater
than 40 microns, wherein the first set of components comprises 35
wt % to 55 wt % alumina particles and 25 wt % to 45 wt % zircon
particles, and wherein the zirconia comprises a first portion
having a larger particle size, the first portion comprising zircon
sand and a second portion having a smaller particle size, the
second portion comprising zircon flour; and providing a colloidal
silica binder at 5 wt % to 10 wt % of the dry weight of the first
set of components, mixing the first set of components with the
colloidal silica binder to form a refractory composition comprising
55 wt % to 65 wt % alumina, 20 wt % to 25 wt % zirconia, and 15 wt
% to 25 wt % silica; and forming a refractory composition on a
surface of a furnace.
Description
FIELD OF THE INVENTION
This invention generally relates to refractory compositions
especially useful for furnaces. More particularly, this invention
relates to colloidal silica refractories for the lining of
furnaces, such as glass and brass furnaces.
BACKGROUND
Glass melting furnaces are refractory lined vessels shaped as
containers for melting and holding glass. In the melting operation,
the incoming glass making materials are heated to about
2800.degree. F. (1550.degree. C.). The glass-making materials
usually include a mixture of cullet and batch materials. Cullet is
crushed glass from the manufacturing process. Batch materials
include sand (silica), lime (limestone or calcium carbonate reduced
to calcium monoxide), soda ash (sodium monoxide), and sometimes
other materials such as feldspar, salt cake, and metal oxides.
During the melting operation, the cullet melts first to increase
the heat transfer to the batch materials and to reduce the melting
time.
Glass melting furnaces include pot furnaces, glass tanks, tank
furnaces, and the like. Glass may be constructed of separate
refractory brick or blocks within a frame. The blocks fit together
without mortar and typically are arranged in a rectangular shape to
hold molten glass. The mechanical pressure from the frame and outer
blocks holds the blocks together. The refractory blocks usually
receive considerable wear from the molten glass and the charging of
glass making materials. Molten glass is highly corrosive. The
refractory blocks usually are made of composite clays having
alumina, zirconia, and silica (AZS). The AZS refractory blocks are
made from molten material cast into molds, which are machined after
hardening. The refractory blocks can become deeply scored and may
develop wear spots or portions where the molten glass has eroded or
dissolved the refractory. The wear spots typically grow until the
refractory fails to hold the molten glass. The wear spots shorten
the service life of glass tanks and often are unpredictable, thus
disrupting production of molten glass.
Brass furnaces are refractory lined vessels shaped as containers
for melting brass. Brass scrap is collected and transported to the
foundry where it is melted in the furnace and recast into billets.
The furnace is also used to heat up billets extruded the brass into
the right form and size. In the melting operation, the incoming
brass-making materials are heated to about 2000.degree. F.
(1100.degree. C.).
SUMMARY
In one aspect, this invention provides a refractory composition
especially useful for furnaces. The refractory composition has been
found to provide excellent corrosion resistance. The refractory
composition includes a first set of components mixed with a
colloidal silica binder. The first set of components includes
alumina and zirconia. The colloidal silica binder is provided at 5
wt % to 20 wt % of the dry weight of the first set of components.
The refractory composition includes 45 wt % to 75 wt % alumina, 15
wt % to 30 wt % zirconia, and 10 wt % to 30 wt % silica.
In another aspect, a method of preparing a refractory includes
providing a first set of components and a colloidal silica binder.
The first set of components includes alumina and zirconia. The
colloidal silica binder is provided at 5 wt % to 20 wt % of the dry
weight of the first set of components. The first set of components
is mixed with the colloidal silica binder to form a refractory
composition including 45 wt % to 75 wt % alumina, 15 wt % to 30 wt
% zirconia, and 10 wt % to 30 wt % silica. The refractory
composition is formed on the surface of a furnace.
The foregoing and other features and advantages of the present
invention will become apparent from the following detailed
description of the presently preferred embodiments, when read in
conjunction with the accompanying examples.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be further described. In the
following passages, different aspects of the invention are defined
in more detail. Each aspect so defined may be combined with any
other aspect or aspects unless clearly indicated to the contrary.
In particular, any feature indicated as being preferred or
advantageous may be combined with any other feature or features
indicated as being preferred or advantageous.
The present invention provides a colloidal silica refractory
composition that is especially useful for glass melting furnaces.
In particular, the refractory composition includes alumina,
zirconia, and silica. The colloidal silica refractory provides
surprisingly good resistance to high temperature corrosive
environments. The refractory composition disclosed herein may also
be used in other types of furnaces, such as brass furnaces.
The refractory comprises a mixture of a colloidal silica binder
with a first set of components. The colloidal silica binder is in
the range of about 5 wt % through about 20 wt % of the dry weight
of the first set of components, preferably between 6 wt % and 12 wt
%, more preferably between 7 wt % and 10 wt %. The first set of
components includes alumina (Al.sub.2O.sub.3), zirconia
(ZrO.sub.2), and silica (SiO.sub.2). The first set of components
may be dry or wet and also may include other minerals, a setting
agent like magnesia (MgO), and/or a flow modifier.
The alumina, zirconia, and silica provide strength and corrosion
resistance. The alumina may be provided by a high aluminum
aggregate such as tabular or white fused alumina. The alumina may
be reactive or calcined. The zirconia may be provided by zircon
flour or a zirconia bearing material. The silica may be provided by
fumed silica, mullite (aluminum silicate), microsilica, colloidal
silica, or the like. The various components are available from
AluChem, Inc. (Reading, Ohio), Alcan, Inc. (Montreal, Canada), and
other conventional suppliers.
The colloidal silica binder holds or binds the first set of
components together in a monolithic form. The colloidal silica
binder includes colloidal silica in water, where the silica is in
the range of about 15 wt % through about 70 wt %. In one
embodiment, the colloidal silica may have an average particle
diameter in the range of about 4 nm through about 100 nm.
In one embodiment, the refractory composition does not include an
effective amount of any other type of binder, such as a hydraulic
cement binder. The refractory composition may include less than 1
wt % hydraulic cement. The refractory composition may include less
than 2%, 1%, 0.5%, or 0.15% CaO or CaCO.sub.3 by weight. Hydraulic
cements typically include lime (CaCO.sub.3) and/or limestone (CaO),
along with other minerals such as alumina and silica. Refractory
materials that include cement tend to be difficult to dry when
setting, especially at lower temperatures. Further, some cement
refractories can generate low melting phases at the high
temperatures typical of glass melting furnaces, thus leading to
higher corrosion rates.
The first set of components may include 30 wt % to 60 wt % alumina,
20 wt % to 50 wt % zircon, 10 wt % to 30% mullite, and up to 10 wt
% silica. The median particle size of the first set of components
may be greater than 40 microns. At least 50 wt % of the first set
of components may include particles greater than 400 microns. It is
known that particle size effects the properties of the liquid
refractory compositions (such as pumpability), as well as the
mechanical and chemical properties of the final refractory. Proper
particle provides good particle packing for reduced porosity, which
leads to greater strength and less glass penetration in the
refractory. The particle size of the refractory material allows for
a multi-functional material which can be easy shotcreted, pumped or
cast.
The first set of components preferably includes less than 15 wt %,
10 wt %, or 5 wt % fused AZS particles, and may include no fused
AZS particles. Fused AZS particles consist of particles each
comprising alumina, zirconia, and silica. In contrast, the present
composition preferably does not include fused AZS particles.
Instead, the first set of components includes particles selected
from alumina, zircon, silica, mullite, and the like.
Preferably, the first set of components includes about 35 wt % to
55 wt % alumina, more preferably 40 wt % to 50 wt % alumina. The
alumina particles preferably have an average particle size greater
than 1 mm. The first set of components may include 30 wt % to 50 wt
% alumina of mesh size 8.times.14 and 2 wt % to 10 wt % alumina of
mesh size -14M. The first set of components may include up to about
5 wt % reactive alumina.
Preferably, the first set of components includes 25 wt % to 45 wt %
zircon, more preferably 30 wt % to 40 wt % zircon. Preferably, the
first set of components includes up to 5 wt % silica, more
preferably up to about 2 wt % silica. The first set of components
may contain no silica. Preferably, the first set of components
includes 15 wt % to 25 wt % mullite.
Other proportions of the first set of components may be used. The
first set of components may include other compounds such as a
setting agent. The first set of components may include about 0.1 wt
% magnesia as a setting agent. The amount of setting agent may be
adjusted to increase or decrease the setting time for the colloidal
system refractory. The first set of components also may include a
flow modifier to enhance or alter the flow properties for forming
the colloidal silica refractory prior to setting. The first set of
components may be mixed prior to the addition of the colloidal
silica binder.
The resulting refractory composition includes about 45 wt % to 75
wt % alumina, 15 wt % to 30 wt % zirconia, and 10 wt % to 30 wt %
silica. The refractory composition may include 50 wt % to 70 wt %
alumina, 55 wt % to 65 wt % alumina, or about 60 wt % alumina. The
refractory composition may include 18 wt % to 27 wt % zirconia, 20
wt % to 25 wt % zirconia, or about 22 wt % zirconia. The refractory
composition may include 12 wt % to 26 wt % silica, 15 wt % to 25 wt
% silica, or about 18 wt % silica.
The refractory composition may be cast into blocks for subsequent
use in a glass tank or other furnace, or may be formed directly
onto the wear portion of a glass tank or other furnace. Besides
glass furnaces, the refractory composition may be used in brass,
copper, and bronze furnaces. The refractory composition may be
formed on the wear portion using one or more refractory forming
methods such as casting, pumping, or shotcreting (formless pumping
with a setting accelerant). The refractory composition may be
formed on one or more portions of the sidewall or hearth. The
refractory composition may be formed directly on the wear portion
without the replacement of refractory blocks in a glass melting
furnace.
EXAMPLES
Example 1
For illustration purposes and not as a limitation, Table 1 provides
exemplary types and proportions of first set of components for the
colloidal silica refractory system.
TABLE-US-00001 TABLE 1 Comparative Mesh Example A Example 1 Raw
Material Size Wt % Wt % Tabular Alumina 8 .times. 14 37.7 30.5
Tabular Alumina -14M 4.7 3.8 Reactive Alumina -325M 4.7 3.8 (e.g.,
CAR 120B) Calcined Alumina -325M 9.4 7.6 (e.g., CAR 60RG) Zircon
Flour -325M 16.5 15.3 Zircon Sand 0 19.1 Fumed silica 2.4 0 White
fused mullite 23.5 19.1 Al powder 0.9 0.8 Surfactant 0.05 0.04 MgO
98% -200M 0.09 0.08
For each Example, the first set of components was mixed together
prior to mixing with the colloidal silica binder. The colloidal
silica binder was provided at a wt % of about 7% to about 10% by
weight of the first set of components. The mixture cured into a
colloidal silica refractory. The formula of Comparative Example A
yielded a refractory containing about 75 wt % alumina, about 11 wt
% zirconia, and about 14 wt % silica. The formula of Example 1
yielded a refractory containing about 60 wt % alumina, about 22 wt
% zirconia, and about 18 wt % silica. Thus, the refractory of
Example 1 had a higher amount of zirconia than the refractory of
the Comparative Example.
To simulate the harsh conditions in a glass melting furnace,
refractory corrosion tests were performed on the colloidal silica
refractories to evaluate their resistance to molten glass. Thin
(0.5 inch diameter) columns or pencils of the refractory
compositions were prepared. The fingers were dipped into molten
glass at a high temperature. The tests were run for 72 hours at
1232.degree. F. After the test, the samples were cooled and
analyzed to determine the resistance of the refractory composition
to the harsh conditions. The test was repeated for each sample for
a total of two tests for each composition. The cross sectional area
of the pencil lost during the test was measured and the results
were averaged. The pencil prepared from the formula of Comparative
Example A lost an average of 65.3% of its cross-sectional area. The
pencil prepared from the formula of Example 1 lost only an average
of 39.6% of its cross-sectional area. Thus, the pencils prepared
from the composition of Example 1 were surprisingly resistant to
corrosion. Thus, the colloidal silica refractories disclosed herein
show superior resistance under harsh conditions compared to a prior
art refractory.
Example 2
To simulate the harsh conditions in a glass melting furnace,
refractory corrosion tests were performed to evaluate resistance to
sodium hexametaphosphate. Thin pencils of the refractory
compositions of Example 1 and Comparative Example A were prepared.
The pencils were dipped into sodium hexametaphosphate at a high
temperature. The tests were run for 48 hours at 1093.degree. C.
(2000.degree. F). After the test, the samples were analyzed to
determine the resistance of the refractory composition to the harsh
conditions. The pencil prepared from the formula of the Comparative
Example lost about 43% of its cross sectional area. The pencil
prepared from the composition of Example 1 was surprisingly
resistant to corrosion and lost less than 8% of its cross sectional
area.
Example 3
A composition prepared according to Example 1 was applied in a
brass furnace. The furnace was operated for a period of time and
the composition was found to perform well throughout the furnace.
Comparative Example B included an alumino-silicate refractory (65%
alumina, 32% silica) applied above the bath line in the furnace and
an alumina-silicon carbide material (74% alumina, 17.5% silicon
carbide, 6% silica) applied below the bath line. For Comparative
Example B, the alumino-silicate product worked well above the bath
line and the alumina-silicon carbide product worked well below the
bath line, but neither material held up at the interface. The
composition of Example 1 showed superior performance to the
composition of Comparative Example B, especially at the bath
line.
Various embodiments of the invention have been described and
illustrated. However, the description and illustrations are by way
of example only. Other embodiments and implementations are possible
within the scope of this invention and will be apparent to those of
ordinary skill in the art. Therefore, the invention is not limited
to the specific details, representative embodiments, and
illustrated examples in this description. Accordingly, the
invention is not to be restricted except in light as necessitated
by the accompanying claims and their equivalents.
* * * * *